Are you talking about this type of panel? See link.

If so, When I talked to EPS guys, At Omaha Ag expo, They told me the cost of the structural, steel insulated panels would be more than the cost of the of the steel building, BUT I have no numbers to qualify that statement.

I really like that idea, of structural steel insulated panels(in one step, the exterior, the insulation, and the interior are attached AND mostly hidden fasteners[depending on type]).
 Personally, I am ok with, the idea of the grits being exposed. That first, lower grit would act as a shelf. BUT, they would also get dusting and probably gain clutter, too= disadvantage.

When I spoke with the gals, at Hardsteel, they said they were looking into those panels, as they have had customers, ask for them, too. (they have a 2.5" shiplap insulation board, that they can double-up , if customer wants it = 5" insulation. This system would require an interior, metal finish panel to complete the shop. [ my worries, on this system, was the exterior steel metal, would require 5.5" screws to hold "in place" . In my thinking, I would think some looseness, "could" occur= I am unsure.]
 Note: I did like Hardsteel "straight, vertical, main framing supports" = seems like more usable space, to me.

I do know of one Hardsteel garage, and that guy likes it.(only 3 miles away, from me) he and his buddies, built it(They were all construction guys, anyways)

http://steelbuildinginsulation.com/foampanels.html


This will be interesting thread to follow.

http://www.hardsteelbuildings.com/